Still doesn't work.
My symptoms do seem very similar to the issue in bug#36725 and I suspect the use-package component mentioned there is just incidental (I also have use-package and it was installation of the delight package, which is used by use-package, which I was using to diagnose this). I also tried the same process on a mcaOS system, same emacs version and it worked with no problems. So, seems to be a TLS issue and restricted to GNU Linux. Will try and update the bug report with this additional info.
thanks Eli.
Tim